Regular articleEvaluating the influences of ZnO engineering nanomaterials on VFA accumulation in sludge anaerobic digestion

- Effect of ZnO ENMs on VFA accumulation was investigated.
- VFA production was negatively correlated with the concentration of ZnO ENMs.
- Less VFA consumed during methanogenesis when more ZnO ENMs were present.
- Zn2+ was one of the main reasons for the impact of ZnO ENMs on sludge anaerobic digestion.

With the increasing use of engineering nanomaterials (ENMs) in industrial and domestic products, ENMs inevitably enter into wastewater treatment plants and remain in sewage sludge. Most of the reported studies on anaerobic digestion were focused on the impact of ENMs on different types of ENMs, methane production, key metabolism enzymes and microorganisms. Little attention was paid to the effect and mechanism of ENMs on volatile fatty acids (VFAs) accumulation during anaerobic digestion. In this work, the concentration of accumulative VFAs during anaerobic digestion with the presence of ZnO ENMs was found to be affected positively compared to the control (without ZnO ENMs). The enhanced VFAs accumulation in the presence of ZnO ENMs was contributed to slowly production and consumption of VFA during anaerobic digestion. Mechanism exploration suggested that impact on protein hydrolysis and change of archaea community structure were the main reasons. Further investigation revealed that Zn2+ is one of the main reasons for the impact of ZnO ENMs on VFA accumulation in sludge anaerobic digestion.